A variety of abrasive and superabrasive tools has been developed over the past century for performing the general function of removing material from a workpiece. Actions such as sawing, drilling, polishing, cleaning, carving, and grinding, are all examples of material removal processes that have become fundamental to a variety of industries.
A number of specific material removal applications require the use of superabrasive tools. In these cases, the use of conventional abrasive tools may be infeasible due to the nature of the workpiece, or the surrounding circumstances of the process. For example, activities such as cutting stone, tile, cement, etc. are often cost prohibitive, if not impossible to accomplish, when attempted using a conventional saw blade. Additionally, the economy and performance of other material removal activities may be increased when using superabrasive tools, due to their greater durability.
Wire saws containing superabrasive particles can provide many benefits over conventional cutting tools. For example, wire saws can cut almost any thickness while circular saws, and the like, are limited to a cutting depth of less than the radius of the blade. Further, the flexibility of superabrasive wire saws allows for cutting of straight or profiled cutting paths. Conventional wire saws are produced by sliding steel beads over a metal wire or cable. The beads are typically separated by spacers and the metal wire is protected by plastic or rubber to prevent corrosion. Such beads are covered by abrasive or superabrasive particles which are commonly attached by either electroplating or sintering. Electroplated beads generally contain a single layer of abrasive particles which are mechanically bonded to the bead. This mechanical bonding allows for premature loss of abrasive particles, thus shortening the useful life of the wire saw. Sintered beads can contain multiple layers of abrasives. Some wire saws can use a resin to bind the abrasives to the wire. Unfortunately, the resin bonded wire saws tend to wear quickly and the abrasives are lost well before the useful life of the particles is realized.
A number of attempts have been made to overcome the above-recited shortcoming. Most notably, several techniques that attempt to chemically bond the superabrasive particles to the matrix, or other substrate material, have been employed. The main focus of such techniques is to coat or otherwise contact the superabrasive particle with a reactive element that is capable of forming a carbide bond between the superabrasive particle and the metal matrix, such as titanium, chromium, tungsten, etc. Examples of specific processes include those disclosed in U.S. Pat. Nos. 3,650,714 4,943,488; 5,024,680; 5,030,276; and 6,102,024, each of which is incorporated herein by reference. However, such processes are difficult and costly for a variety of reasons, including the highly inert nature of most superabrasive particles, and the high melting point of most reactive materials. Additionally, the direct brazing of superabrasive particles to the metal wire reduces the flexibility of the wire saw and the braze coating becomes susceptible to fatigue and premature failure.
Further, the melting point of most reactive metal materials is well above the stability threshold temperature of most superabrasives. To this end, the method by which the reactive material may be applied to the superabrasives is generally limited to either solid-state reactions or gas reactions that are carried out at a temperature that is sufficiently low so that damage to the diamond does not occur. Such processes are only capable of achieving a monolithic coating, and cannot produce an alloy coating. While the strength of the carbide bonds yielded using these techniques generally improves particle retention over mere mechanical bonds, they still allow superabrasive particles to become dislodged prematurely.
Another method of forming carbide bonds is by using a braze alloy that contains a reactive element. The braze alloy is consolidated around the superabrasive particles by sintering. One example of a specific process of this type is found in U.S. Pat. No. 6,238,280, which is incorporated herein by reference. While such processes may yield a tool that has greater grit retention than tools having no chemical bonding of the superabrasive particles, as a general matter, solid-state sintering of the braze alloy only consolidates the matrix material, and does not attain as much chemical bonding as the solid and gas state deposition techniques.
As such, superabrasive wire saws that display improved superabrasive particle retention and wear characteristics, including methods for the production thereof, continue to be sought through ongoing research and development efforts.